U.S. patent application number 12/361806 was filed with the patent office on 2009-07-30 for dynamometric tool for medical use.
This patent application is currently assigned to HADER SA. Invention is credited to Silver GROSS, Philippe MILETTO.
Application Number | 20090192517 12/361806 |
Document ID | / |
Family ID | 39539570 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090192517 |
Kind Code |
A1 |
MILETTO; Philippe ; et
al. |
July 30, 2009 |
DYNAMOMETRIC TOOL FOR MEDICAL USE
Abstract
A dynamometric tool for medical use with a longitudinal axis AA
includes: a hollow grip (10) including an interior wall having a
succession of recesses (29) oriented along the axis AA and the
section of which is egg-shaped, an instrument holder (30) to be
secured in rotation with an instrument configured to cooperate with
an object to be screwed, the instrument holder being extended by a
shaft (18) with an axis AA pivoting inside the grip. The instrument
holder (30) is frictionally connected to the grip using a plurality
of elastic members (2) arranged between the shaft (18) and the grip
(10), each elastic member (2) including a plurality of blades (4)
arranged primarily along non-radial directions and elastically
deformable along an essentially radial direction, the ends of the
blades forming skids designed to cooperate with the recesses (29)
of the interior wall.
Inventors: |
MILETTO; Philippe; (Orny,
CH) ; GROSS; Silver; (La Chaux-deFonds, CH) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
HADER SA
La Chaux-de-Fonds
CH
|
Family ID: |
39539570 |
Appl. No.: |
12/361806 |
Filed: |
January 29, 2009 |
Current U.S.
Class: |
606/104 |
Current CPC
Class: |
A61B 17/8875 20130101;
A61B 2090/031 20160201; B25B 23/1427 20130101; A61C 1/186 20130101;
A61C 8/0089 20130101 |
Class at
Publication: |
606/104 |
International
Class: |
A61B 17/58 20060101
A61B017/58 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2008 |
EP |
08101067.0 |
Claims
1. A dynamometric tool for medical use with a longitudinal axis AA
comprising: a hollow grip including an interior wall having a
succession of recesses oriented along the axis AA and the section
of which is egg-shaped, an instrument holder to be secured in
rotation with an instrument configured to cooperate with an object
to be screwed, said instrument holder being extended by a shaft
with an axis AA pivoting inside the grip, said instrument holder
being frictionally connected to said grip using a plurality of
elastic members arranged between said shaft and said grip, each
elastic member comprising a plurality of blades arranged primarily
along non-radial directions and elastically deformable along an
essentially radial direction, the ends of the blades forming skids
designed to cooperate with said recesses of said interior wall,
wherein the recesses succeed each other without interruption, such
that, between two consecutive recesses, there is no surface
allowing a skid to occupy a stable position.
2. The tool of claim 1, wherein said skids are cylindrical in shape
and are designed to be substantially parallel to said shaft.
3. The tool of claim 1, wherein said elastic members are mounted
idle on the shaft and have play between the shaft and said elastic
members, on one hand, and between said elastic members and said
interior wall, on the other hand.
4. The tool of claim 2, wherein said elastic members are mounted
idle on the shaft and have play between the shaft and said elastic
members, on one hand, and between said elastic members and said
interior wall, on the other hand.
5. The tool of claim 3, wherein the play between said skids and
said recesses is between 2 and 15 hundredths of millimeters,
preferably between 5 and 10 hundredths of millimeters, when the
tool is at rest, and in that the play between said shaft and said
elastic members is typically between 1 and 5 hundredths of
millimeters, preferably 3 hundredths of millimeters, when the tool
is at rest.
6. The tool of claim 4, wherein the play between said skids and
said recesses is between 2 and 15 hundredths of millimeters,
preferably between 5 and 10 hundredths of millimeters, when the
tool is at rest, and in that the play between said shaft and said
elastic members is typically between 1 and 5 hundredths of
millimeters, preferably 3 hundredths of millimeters, when the tool
is at rest.
7. The tool of claim 1, wherein said shaft is mounted pivoting in
the grip using at least first and second bearings, adjusted in the
grip, the shaft being adjusted in said bearings, said elastic
members being mounted on the shaft, between said bearings.
8. The tool of claim 2, wherein said shaft is mounted pivoting in
the grip using at least first and second bearings, adjusted in the
grip, the shaft being adjusted in said bearings, said elastic
members being mounted on the shaft, between said bearings.
9. The tool of claim 3, wherein said shaft is mounted pivoting in
the grip using at least first and second bearings, adjusted in the
grip, the shaft being adjusted in said bearings, said elastic
members being mounted on the shaft, between said bearings.
10. The tool of claim 5, wherein said shaft is mounted pivoting in
the grip using at least first and second bearings, adjusted in the
grip, the shaft being adjusted in said bearings, said elastic
members being mounted on the shaft, between said bearings.
11. The tool of claim 7, wherein the first bearing is mounted
abutting inside said channel, the second bearing being screwed onto
the grip.
12. The tool according to claim 1, wherein said elastic members
comprise a hub realized in a material which is not elastically
deformable and a bushing supporting the blades and mounted secured
around the hub.
13. The tool according to claim 1, wherein the elastic blades are
realized in PEEK.
14. The tool of claim 12, wherein the elastic blades are realized
in PEEK.
15. The tool according to claim 1, wherein the interior wall of
said channel is in PEEK.
16. The tool of claim 12, wherein the interior wall of said channel
is in PEEK.
17. The tool according to claim 1, wherein the grip is in PEEK.
18. The tool of claim 12, wherein the grip is in PEEK.
19. The tool according to claim 12, in which the elastic blades are
each made up of a steel tab, secured by a first of their ends in a
groove arranged in the hub, along a longitudinal axis thereof, and
comprises, at their second end, said skid.
Description
TECHNICAL FIELD
[0001] The present invention relates to the field of tools for
medical use. It more particularly concerns a dynamometric tool
designed to tighten and loosen screws or various objects comprising
a screw pitch, typically during a surgical operation.
[0002] It is, indeed, particularly important to avoid applying
uncontrolled tightening torques, for example in the case where a
plate is fixed on a bone to repair a fracture. If the tightening
applied is excessive, this can lead to crushing the bone and
damaging it further.
PRIOR ART
[0003] One knows, in the prior art, dynamometric tools for
screwing, and sometimes unscrewing, of various objects, in
particular screws for fixing reconstruction elements in plastic
surgery. As an example of application, plates can be screwed into
fractured bones in order to facilitate their healing. A tool of
this type comprises: [0004] a grip so that the surgeon can
manipulate it, and [0005] an instrument holder to be secured in
rotation with an instrument configured to cooperate with the object
to be screwed.
[0006] There are two main types of dynamometric tools. A first
provides a limitation of the tightening torque, through the
establishment of a safety stop which makes the grip and the
instrument holder secured in rotation as long as the selected
maximum torque is not reached and which stops when a determined
tensile strength corresponding to the maximum torque is reached.
This type of tool is described, for example, in document U.S. Pat.
No. 5,368,480. A torque limiting member is inserted between the
grip and the instrument holder. This member comprises a plurality
of lugs dimensioned so as to form the abovementioned stop and to
collapse when the desired tightening torque is reached.
[0007] However, these lugs undergo a plastic deformation, i.e.
irreversible, the result of which is that each of the lugs can only
be used a single time. Of course, the fact that the torque limiting
member comprises a plurality of lugs makes it possible to perform
several tightenings at maximum torque, but only a very limited
number. Moreover, it is difficult to precisely control the maximum
tightening torque, because the plastic deformation threshold
depends on a large number of parameters and can be influenced by
slight differences having taken place during manufacturing of the
torque limiting member.
[0008] The second type of dynamometric tools makes it possible to
perform a large number of tightenings at the maximum torque,
without having to intervene on the tool, thanks to a sort of
snapping system. In certain tools of this type, the instrument
holder is extended by a shaft pivoting in the grip, the shaft being
frictionally connected to the grip. The friction is provided by two
Breguet toothings, i.e. saw-shaped serrated toothings, one being
integral with the instrument holder and the other being integral in
rotation with the grip. Springs press the two Breguet toothings
against each other so as to make the instrument holder and the grip
integral in rotation. When the tightening torque is greater than
the friction imposed between the two Breguet toothings by the
springs, the latter parts rub against each other and escape. The
instrument holder is then no longer driven in rotation by the grip.
The maximum applicable tightening torque can be adjusted by
modulating the pressure exerted by the springs.
[0009] The friction created between the toothings is particularly
significant and it is necessary, in order to obtain acceptable
precision and longevity of the tool, for the Breguet toothings to
be metal. They, as well as the springs, are made in stainless
steel, allowing surgical use which is as hygienic as possible. It
is, however, necessary to grease the metallic parts in friction,
which is not very satisfactory from a sanitary perspective, since a
risk of grease flow outside the tool exists during sterilization
operations. Moreover, the precision of such a tool is not very
satisfactory (.+-.10%) and it is necessary to perform calibrations
regularly.
[0010] Furthermore, when the maximal tightening torque is reached
and the toothings escape each other, this causes jumps in the
longitudinal direction of the tool, which is not pleasant for the
surgeon and can cause him to make a clumsy gestures. Moreover, the
materials used to produce this tool make it heavy and not very
practical.
[0011] The present invention concerns dynamometric tools of the
second type, making it possible to perform a large number of
tightenings at the maximum torque, without intervention on the
tool. The aim sought is to propose a dynamometric tool free of the
aforementioned drawbacks and which, in particular, is precise,
light, easy to manipulate. Furthermore, the invention also aims to
propose an improved tool, the maximum tightening torque of which is
not affected by the treatments undergone during the sterilization
process.
BRIEF DESCRIPTION OF THE INVENTION
[0012] More precisely, the invention concerns a dynamometric tool
for medical use, with a longitudinal axis AA comprising: [0013] a
hollow grip comprising an interior wall having a succession of
recesses oriented along the axis AA and the section of which is
egg-shaped, [0014] an instrument holder to be secured in rotation
with an instrument configured to cooperate with an object to be
screwed, said instrument holder being extended by a shaft with axis
AA pivoting inside the grip.
[0015] The instrument holder is frictionally connected to the grip
using a plurality of elastic members arranged between the shaft and
the grip. Each elastic member comprises a plurality of blades
arranged primarily along non-radial directions and which are
elastically deformable along an essentially radial direction, the
ends of the blades forming skids designed to cooperate with the
recesses of the interior wall.
[0016] According to the invention, in order to avoid the expansion
caused by heating from sterilization causing a modification of the
elastic properties of the elastic members and an upset of the
maximum tightening torque, the recesses succeed each other without
interruption, such that, between two consecutive recesses, there is
no surface allowing a skid to occupy a stable position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Other details will appear more clearly upon reading the
following description, done in reference to the appended drawings,
in which:
[0018] FIG. 1 is a transverse cross-section of the grip and an
elastic member particularly adapted for the implementation of the
invention, the figure including a close-up showing the interaction
between the grip and an elastic member in detail, and
[0019] FIG. 2 is a longitudinal cross-section of the device
according to the invention of a zone of this part, and
[0020] FIGS. 3 and 4 show, in top view and perspective view, an
embodiment of an elastic member which can advantageously be used in
the tool according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The dynamometric tool according to the invention implements
a torque limiting member which is an elastic member 2 illustrated
in FIG. 1. The elastic member 2 is generally cylindrical in shape
and comprises, in its center, an opening 6 structured so as to have
a non-circular section, not elastically deformable, and forming a
female member.
[0022] More particularly, the elastic member 2 comprises a
plurality of blades 4 whereof the shape, given the material used,
is determined such that they are elastically deformable along an
essentially radial direction. These blades 4 are oriented toward
the outside, primarily along non-radial directions and end, in one
preferred embodiment, with a skid comprising, for example, a
cylindrical portion 4a substantially orthogonal to the general
plane of the elastic member. As one will understand below, it is
the elastic deformation of the blades which makes it possible to
obtain the limiting of the torque. Contrary to a torque limiting
member of the prior art which deforms plastically, the elastic
member 2 used in the invention does not undergo any irreversible
transformation when the maximum torque is reached.
[0023] As one can see in FIG. 1, the opening 6 can also be arranged
in a hub 8 realized using a second piece, integral with a bushing 9
supporting the blades 4. The hub is advantageously realized in a
material which is not elastically deformable, for example of the
metal type, such as a stainless steel.
[0024] FIG. 2 shows a grip 10, with a longitudinal axis AA, topped
with a handle 11. Along this axis, the body 10 is passed through by
a cylindrical channel 12. The latter part comprises a stop 13
designed to provide support for a first bearing 14, having, in its
center, a housing 16 to receive a shaft 18, which will be described
in detail below. The shaft 18 can comprise, at its end, a tapping
20 with axis AA designed to cooperate with a screw in order to
secure it to the bearing 14. One can, for example, access the screw
from the end of the grip.
[0025] The second end of the grip 10 is provided with a screw pitch
10b in order to cooperate with a second bearing 22, provided in its
center with an opening 24 in which the shaft is adjusted.
[0026] At each of the bearings 14 and 22, joints 26 can be inserted
between the bearing and the grip 10, on one hand, and between the
bearing and the shaft 18, on the other hand.
[0027] We have also illustrated, in FIG. 2, an instrument holder 30
of the type known by one skilled in the art, likely to be secured
in rotation to an instrument configured to cooperate with an object
to be screwed. The part of the instrument holder providing the
connection with the instrument is not in itself part of the
invention and will not be described in detail.
[0028] The instrument holder 30 is extended by the shaft 18
previously mentioned. This is dimensioned so as to be able to go
through the opening 24, assume a position in the channel 12 of the
grip 10, while its free end assumes a position in the housing 16.
More specifically, the shaft 18 comprises a first portion 18a
adjusted to the dimension of the opening 24. Then, when going away
from the part of the instrument holder designed to receive an
instrument, a second portion 18b designed to be housed in the
channel 12. The second portion 18b is structured so as to have a
non-circular section, and thereby forms a male member able to be
connected in rotation with the female member of the elastic member
2, which has a corresponding shape. Lastly, the shaft ends with a
third portion 18c adjusted to the dimensions of the housing 16.
[0029] The instrument holder 30 is designed to be mounted pivoting,
frictionally, in the channel 12, using a plurality of elastic
members 2 mounted on the shaft 18 between the two bearings 14 and
22, interposed between the shaft 18 and the wall of the channel
12.
[0030] In order to ensure the friction between the grip 10 and the
elastic members 2, the interior wall of the channel 12 has a
succession of recesses 29, oriented along the axis AA and whereof
the section, visible in FIG. 1 and particularly in the close-up
view, is egg-shaped. The recesses 29 occupy the entire length of
the channel 12 between the two bearings 14 and 22, and are designed
to receive the skids.
[0031] The cylindrical portions 4a are thereby defined so as to
cooperate with the recesses 29 of the channel 12. Other forms may
be chosen as long as the ends of the blades 4 are able to cooperate
with the structures of the wall of the channel 12 to create a
friction likely to stress the elastic blades 4. More particularly,
it is the stress which it is necessary to apply on the elastic
blades 4 so that they go from one recess to the other which
determines the maximum tightening torque.
[0032] It has been noted that tools having the abovementioned
characteristics could undergo fluctuations of their maximum
tightening torque after they had undergone sterilization
treatments. To offset this drawback, one of the important aspects
of the invention illustrated in the close-up of FIG. 1, the
recesses succeed each other without interruption, such that,
between two consecutive recesses 29, there is no surface allowing a
skid to occupy a stable position. In other words, the interior wall
of the channel 12 is configured such that only the recesses 29 can
receive the skids stably. The zone which can be defined between two
recesses is arranged so as not to allow the skids to rest there
stably. Indeed, if this characteristic is not respected, the
elastic members 2 can be positioned stably with the skids resting
between two recesses 29. Naturally, in such a position, the elastic
blades 4 are stressed. If sterilization is done while the elastic
members are thus stressed, their expansion caused by heating from
the sterilization causes a modification of the elastic properties
of the members 2 and an upset of the maximum tightening torque.
[0033] Furthermore, the elastic members 2 are mounted on the shaft
18, integral in rotation but with play. First of all, one will
ensure that play remains between the male member formed by the
shaft 18 and the female member formed by the opening 6. This play
is typically between 1 and 5 hundredths, preferably 3 hundredths.
Then, a clearance J between 2 and 15 hundredths of millimeters,
preferably between 5 and 10 hundredths is provided between the
skids and the recesses 29, when the elastic members are at rest.
One will note that the elastic members 2 will not be idle on the
shaft if they only have one play between the male and female
members. Indeed, in such a case, the blades 4 would press on the
interior wall of the channel 12, which would maintain the elastic
members. The combination of these plays makes it possible to avoid
any hyperstaticity phenomenon in the elastic members 2. Thus, when,
during the sterilization steps, the elastic members 2 expand under
the effect of the heat, this deformation takes place freely,
without creating excessive stress on the elastic members which,
after cooling, keep all of their elastic and nominal properties.
The maximum tightening torque is thus perfectly conserved.
[0034] In order to obtain perfect alignment of the elastic members
2 in reference to the axis AA and the grip 10, despite the
aforementioned plays, the role and precision of the bearings 14 and
22 are important. Indeed, only the bearings serve as guide element
for the shaft 18. Moreover, by its screwing, the second bearing 22
positions the elastic members 2 along the axis AA.
[0035] The elastic members 2 are advantageously realized in a
material not requiring lubrication and resisting the usual
sterilization treatments, thermal and by radiation. Various tests
have made it possible to demonstrate that polymers of the
polyether-ether-ketone type (known under the name PEEK) had the
necessary characteristics. One could more precisely choose PEEK
151G. One could also realize the grip 10 in PEEK, or coat the
interior wall of the channel 12 with it, the elastic members being
realized in another material able to have suitable elastic
properties, in stainless steel, for instance. One skilled in the
art could also consider realizing the elastic members, on one hand,
and the grip on the other, in a single material not requiring
lubrication. One such possibility is particularly advantageous
insofar as it eliminates all difficulties related to differences in
the expansion coefficient between the elastic members 2 and the
grip 10.
[0036] Typically, elastic members as described above and made in
PEEK make it possible to obtain tightening torque values in the
vicinity of several N.m, typically between 0.5 and 15 N.m.
[0037] Thus is obtained a tool whereof the adjustment of the
maximum tightening torque can be particularly precise, with an
improved lifespan. Not only does the tool have the advantages of
certain tools of the prior art, namely that the precision achieved
is in the vicinity of 3% for 10,000 releases. A release is defined
as being the moment when the grip separates from the instrument
holder, going from a first to a second relative position of one of
these elements in relation to the other.
[0038] FIGS. 3 and 4 show one particular embodiment of an elastic
member 2 which can be used in a tool according to the invention. An
elastic member of this type comprises a hub 8 which is cylindrical
in shape, the inner wall of which is dimensioned and configured
similarly to what was previously described. The outer wall
comprises, regularly distributed on its entire perimeter, grooves
32 arranged along the longitudinal axis of the hub and oriented, in
the direction of their depth, along a non-radial direction. More
particularly, the grooves 32 all have an identical orientation
relative to the hub 8. Preferably, each groove occupies the entire
height of the hub.
[0039] In this embodiment, the elastic blades 4 are each made up of
a steel tab, having a rectangular shape, a first end of which is
housed in each groove. The grooves 32 are dimensioned such that the
tabs are housed without play in the grooves. The tabs are fixed,
for example by welding, in the grooves. At their other end, the
blades receive a cylinder 4a forming a skid, the cylinder being
molded from a casting, for example, and produced in PEEK or in a
similar material not requiring lubrication and resisting the usual
sterilization treatments, thermal and by radiation.
[0040] An elastic member of this type has a particularly
interesting reactivity, which is to say that the blades react
particularly quickly going from one recess to the next, which
allows excellent control of the frictional torque, even in case of
quick actuation of the tool. Furthermore, a member of this type
allows the application of a more significant force, increased by
approximately 50% relative to a member with PEEK blades of the same
dimensions.
[0041] One will also note that, with a grip whereof the inner wall
is provided with thirty-six recesses 29, it is possible to use
elastic members provided with 12 or 18 elastic blades, which makes
it possible, with a single tool, to obtain torques of k or with a
value of 1.5 k, simply by changing elastic members. It has been
possible through tests to verify that elastic members of this type
keep a constant torque for 50,000 releases.
[0042] Thus, the tool according to the invention does not need to
be lubricated and can be sealed, avoiding all risk of contamination
of the patient. Moreover, it has the essential advantage of
behaving particularly well during heating related to sterilization
operations. Even after repeated heating cycles, the maximum torque
calibrated in the factory remains unchanged, this guarantees
extremely safe and secure use.
* * * * *